Director Svensson in Stockholm is going on vacation to Koön in the archipelago. The rented cottage is inhabited by the brothers August and Johan Österman. Johan throws out August and tells him to arrange accommodation for the summer guests elsewhere.
The landlubber Stig-Helmer and his Norwegian friend Ole get on a barge by mistake. They arrive at an archipelago and have to spend Midsummer among the fancy rich boat people, their yachts and summer houses.
After getting pregnant from a one-night stand, a single woman leans on her married best friend and mother of two to guide her through gestation and beyond.
Three manic idiots—a lawyer, a cab driver and a handyman—team up to run a ballet company to fulfil the will of a millionaire. Stooge-like antics result as the trio try to outwit the rich widow and her scheming big-shot lawyer, who also wants to run the ballet.
Father-to-be Alan is shocked to learn that he was born a sextuplet. With his newfound brother Russell riding shotgun, the duo sets out on a hilarious journey to reunite with their remaining long-lost siblings.